Passive solar energy

At present, solar energy could be characterized as passive solar strategy and active solar strategy depending on the way they converted into another type of energy. The majority of passive solar design of buildings are based on the thermal mass which is a certain type of material that could store heat for some time. It is achieved by its high thermal resistance. This kind of strategy is suitable for countries with large temperature difference between day and night when it could block the overheating from sunshine in daytime and release the heat to inside room during the night (Figure 1).

                                Figure 1. Thermal mass in day and night in solar chimney 

Figure 2. Working process of solar chimney

In fact, the most famous passive solar strategy is known as solar chimney which could both be used in passive way or active way.  Basically, it is a wall with one side of glass which is positioned toward the Sun. And other sides of the wall are made of thermal mass. Normally, there are two vents in the wall between the inside room and the chimney. During the day, the two vents are open. The sunshine heats up the air inside the chimney. So the air inside the chimney should be warmer than the room air and it would rise vertically through the chimney to inside space based on buoyancy influence. And the cold air on the basement would keep adding into the chimney that induces an simple ventilation system for the whole building. In the night, the two vents would be closed in order to maintain heat in the building.

Figure 3. Passive solar lighting

The sunshine could also be used for lighting during the daytime directly. It is known as "Sun-Pipes" which is fully glazed and adjusted to suitable angle to let the light to coming into the room for lighting through reflecting. The pipes are normally installed on the roof that oriented to South, and the mirrors inside the pipes have a high reflecting capacity  which allows the natural daylight to access into the room deep inside the building.
In fact, passive solar strategy is the way of using solar energy without any kinds of mechanisms supplied or exported by electricity. Passive solar strategies would save a lot of energy for heating and lighting during the day. However, the drawbacks of them are represented to be obvious as they highly depends on the Climate.

Reference

ENERGY. GOV (2012). Passive Solar Home Design  [available online]<http://energy.gov/energysaver/articles/passive-solar-home-design>

ECO-WISE (2012). Passive Solar Design: Sustainable Sources-18 years of online Green Building information.  [available online]
<http://passivesolar.sustainablesources.com>


Alfredo Fernandez-Gonzalez  et al.(2012)  SIMPLICITY AND INTEGRATION: PASSIVE SOLAR DESIGN AND PASSIVE HOUSE  

IN INTEGRATED PRACTICE AND EDUCATION 

Planet Energy Solutions (2010) Passive solar lighting [available from]
<http://www.planetenergy.co.uk/Solar%20lighting%20information%20sheet.pdf>